Exploration of the eastern Alaska North Slope has focused increasingly on stratigraphic objectives in the predominately Tertiary “Brookian Sequence”, a syntectonic elastic wedge derived from the Brooks Range and deposited in a foreland basin south of, and on a rifted continental margin north of, the Early Cretaceous Barrow Arch. In ANWR, Brookian strata comprise several depositional sequences identified with seismic data based on recognition of unconformities and correlative conformities. These sequences record the growing influence of synsedimentary tectonism on accommodation space during Tertiary deposition.

Although Tertiary strata onlap the Barrow Arch, widespread depositional sequences of Paleocene-Eocene age display seismic facies indicating eastward progradation of clinoforms inboard of the buried arch and accumulation of thick basin plain facies outboard, suggesting a residual accommodation effect. An exception is an apparently structurally transposed piggyback basin in which Late Cretaceous-Paleocene depositional sequences display thickness trends suggesting localized synsedimentary uplift.

Depositional sequences of Oligocene-Miocene age reflect growing influence of synsedimentary uplifts and diminished residual influence of the Barrow Arch. In western ANWR, strata are undeformed and seismic facies suggest northward clinoform progradation and maximum sediment accumulation accompanied by active growth faulting offshore. Eastern ANWR is segmented into syntectonic sub-basins separated by uplifts involving strata as young as Eocene. Depositional sequences of Oligocene-Miocene age thin over uplifts and thicken into sub-basins. Proximal (south) sub-basins are filled with topsets, whereas distal (north) sub-basins contain progradational clinoforms.

Potential stratigraphic traps in Brookian strata are influenced by residual accommodation effects of presedimentary tectonics and by local synsedimentary tectonics. These influences must be reconciled with the widespread influences of eustacy for assessing the potential of stratigraphic accumulations.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah